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<title>VFK - Czech Cadastral Exchange Data Format</title>
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<h1>VFK - Czech Cadastral Exchange Data Format</h1>

This driver reads VFK files, ie. data in the <em>Czech cadastral
exchange data format</em>. The VFK file is recognized as an OGR
datasource with zero or more OGR layers. The filenames must end with
.vfk extension.

<p>
Note: starting with OGR 1.10, the driver is compiled only if GDAL
is <em>built with SQLite support</em>.

<p>
Points are represented as wkbPoints, lines and boundaries as
wkbLineStrings and areas as wkbPolygons. wkbMulti* primitives are not
used. Feature types cannot be mixed in one layer.

<h3>Configuration</h3>

Starting with OGR 1.9, the driver reads and writes VFK data from/to
internal SQLite database. Default name of the database is
&lt;input_vfk_file&gt;.db. Since OGR 1.10, you can define an
alternative DB name with <tt>OGR_VFK_DB_NAME</tt> configuration
option. If <tt>OGR_VFK_DB_OVERWRITE=YES</tt> configuration option is
given, than the driver overwrites existing SQLite database and reads
data from original input VFK file.

<p>
Starting with OGR 1.10, resolved geometries are stored also in SQLite
database. It means that geometries are resolved only once when
building SQLite database from original VFK data. Geometries are stored
in WKB format. Note that GDAL doesn't need to be built with SpatiaLite
support. Geometries are not stored in DB
when <tt>OGR_VFK_DB_SPATIAL=NO</tt> configuration option is given. In
this case the geometries are resolved from DB.

<h3>Internal working and performance tweaking</h3>

Since OGR 1.9, the driver will use an internal SQLite database to
resolve geometries. By default, this file will be written in the same
directory as input VFK file. If SQLite database already exists then
the driver reads VFK features directly from database (and not from
original VFK file).

<h2>Datasource name</h2>

Datasource name is a full path to the VFK file.

<h2>Layer names</h2>

VFK data blocks are used as layer names.

<h2>Filters</h2>

<h3>Attribute filter</h3>

OGR internal SQL engine is used to evaluate the expression. Evaluation
is done once when the attribute filter is set.

<h3>Spatial filter</h3>

Bounding boxes of features stored in topology structure are used to
evaluate if a features matches current spatial filter. Evaluation is
done once when the spatial filter is set.

<h2>References</h2>

<ul>
<li> <a href="http://geo.fsv.cvut.cz/~landa/publications/2010/gis-ostrava-2010/paper/landa-ogr-vfk.pdf">OGR
VFK Driver Implementation Issues</a></li>
<li> <a href="http://grass.fsv.cvut.cz/gwiki/VFK">Open Source Tools for VFK format</a> (in Czech)</li>
<li> <a href="http://www.cuzk.cz/Dokument.aspx?PRARESKOD=998&MENUID=0&AKCE=DOC:10-VF_ISKNTEXT">Czech
cadastral exchange data format documentation</a> (in Czech)</li>
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